Background

Hypereosinophilic syndrome varies from an asymptomatic phenomenon to a life-threatening multisystem disease. It is characterized by an eosinophil count of more than 1500/μ L (usually many more) for more than 6 months and multiorgan involvement in the absence of other causes of eosinophilia and in the absence of eosinophil blast cells in the marrow or blood.
[1] Three subtypes are recognized: myeloproliferative, lymphocytic, and idiopathic.
[2] Hypereosinophilic syndrome is very rare in children.

FIP1L1/PDGFR point mutations often camouflage assays of TK activity, but do not necessarily affect imatinib effectiveness.
[4]

Eosinophilic esophagitis is associated with genetically based loss of esophageal tissue differentiation, with both up and down regulation of proteases and their inhibitors.
[5]

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Epidemiology

Frequency

Worldwide, hypereosinophilia is rare, especially in children.

Mortality/Morbidity

Death generally results from primary heart damage or secondary endocarditis. Survival is prolonged if the sequelae of organ damage, especially cardiac organ damage, can be controlled. Mean survival is 9 months; the 3-year survival rate is reported to be 12%.

Poor prognostic indicators include the following:

Anemia

Thrombocytopenia

A WBC count higher than 100,000 cells/μ L

Abnormal circulating basophilic cells

Abnormal bone marrow

An elevated vitamin B-12 level

Abnormal leukocyte alkaline phosphatase levels

Race

The prevalence is low, with a racial distribution of cases as follows: 78% whites, 18% blacks, and 4% Asian Americans.

Sex

Hypereosinophilic syndrome has a 55.3% male predominance in the pediatric population.
[6] The male-to-female ratio is 9:1 in adults.

Age

Persons aged 5-80 years can have hypereosinophilic syndrome. Persons aged 41-50 years are most commonly affected. The disease is rare in children.

One report documents a case of eosinophilia (WBC count, 80,000/μ L with 63% eosinophils) in an infant born to a mother with hypereosinophilic syndrome.
[7] The child's eosinophil count returned to normal in 8 months.